In recent years, the network which has a communication form where data is transmitted and received freely among the any nodes constituting a network has come into popular use.
As a typical form, there is a form of the communication network called P2P (Peer to Peer). P2P is a usage form of the network, which exchanges information directly among a plurality of unspecified nodes. There are two kinds of P2P. One kind of P2P technically requires mediation of a central server and the other kind of P2P transfers data with a bucket brigade system.
In the network configuration of such distributed processing, in order to execute direct connection between any nodes and to transmit and receive file information, a degree of freedom in communication was improved and it became convenient. On the other hand, there was a tendency to increase danger in the security matter, such as exploitation of file information by a third party and careless data outflow.
When communicating between nodes by a direct connection, the technology where a corresponding node is authenticated using an encryption process and a signature, has been employed in order to improve security.
In addition, generally, a plurality of nodes which configure a network forms a workgroup, where the nodes (logged) in the workgroup verify that they are logged in the same workgroup using a password, and they thus permit each other to access.
However, also in this case, when the node communicates with a plurality of nodes of the same workgroup, the node had to be subjected to password-based-authentication each time the node accessed each node in order to secure security.
In order to perform such password-based-authentication, there was also a case in which plurality of exchanges are needed. In addition, the input operation took much time and effort, and verification took time. Therefore, these were troublesome.
In order to efficiently attain such a mutual authentication process, a technology to simplify the authentication process by issuing an authentication ticket has been proposed (refer to Unexamined Japanese Patent Application Publications Nos. 2001-134534, 2003-85141 and 2003-296277).
In Unexamined Japanese Patent Application Publication No. 2001-134534, disclosed is a technique where the information encrypted by the public key of the server stored in a certificate authority proxy server is sent to the sever through an authentication proxy sever when the server authenticates the client. However, with this technology, a communication is always conducted through the certificate authority proxy server. A communication is not completed by the direct communication between any nodes.
In Unexamined Japanese Patent Application Publication No. 2003-85141, disclosed is a type of a technology in which an authentication system first authenticates a user, and then the system issues a ticket. However, this system has the form in which the authentication system exist between the service providing system and the user, and a direct connection between any nodes is not intended to be implemented.
In Unexamined Japanese Patent Application Publication No. 2003-296277, proposed is a method in which a non-logged in node gets an authentication ticket from a network device (WWW application) which the non-logged in node has accessed. This system has an authentication server separately, which authenticates the non-logged in node. However, in this technology, only the communication to a particular WWW application is conducted using the authentication ticket, and an inquiry to the authentication server is required every time a communication between any nodes is conducted. It is troublesome to use the authentication ticket this way.
Therefore, in order to communicate by directly connecting between any nodes in a distributed processing network, there is especially desired a usage form of the authentication ticket in which an authentication process including a verification of passwords for getting logged in, in other word, accessing each of the logged in nodes can be simplified and can be efficiently executed.